A need has long existed to restrict access by persons to machines such as automated teller machines (ATMS) or computers, places such as workplace office buildings or laboratories, and data such as personal bank accounts or corporate intellectual property. Over time, a number of techniques have been devised to answer this need.
Passwords or PINs (personal identification numbers) have long been used in restricting access to computers, ATMS, rooms in buildings, various types of accounts on internet websites or personal data, such as credit card or bank account information over a telephone or by way of a computer. Passwords can be effective when they are chosen carefully and carefully maintained in secret. However, it is all too common for passwords to be chosen that are all too easy for others to guess or to crack with software to be chosen, such as the name of one's pet or a nickname for a family member. It is also all too common for passwords to be shared with trusted friends or coworkers, or to be written someplace where they can be easily found, such as on a sheet of paper inside a desk drawer.
Security tokens carrying some form of unique identifier, such as badge reader cards with a magnetic stripe or other devices using radio frequency emissions have long been used, especially in restricting access to places such as workplaces or rooms within workplaces where information or equipment of high value is maintained. However, such security tokens can be lost by or stolen from the persons for whom they were intended, and until such a loss or theft is reported so that the security token may be deactivated, it is possible that the security token may be used to provide access to someone who is not meant to have it. It is also possible that the person to whom a security token has been provided may voluntarily give it to someone else, such as a coworker to let them gain access to something or some place as a favor.
More recently, technology has made possible the identification of specific persons by way of biometric readings such as finger print, palm print or retinal scans. Although such biometric-based techniques go far in ensuring the provision of access to only designated persons, the use of such technology is often too prohibitively expensive to provide each machine, door, etc., with a biometric reading device.